Optical imaging system

ABSTRACT

An optical imaging system includes a first lens having positive refractive power and having a convex object-side surface; a second lens having negative refractive power; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having refractive power; a sixth lens having positive refractive power and having a convex image-side surface; and a seventh lens having negative refractive power and having a concave image-side surface, and the first to seventh lenses are disposed in order from an object side. In the optical imaging system, 1&lt;f/f6 and V2&lt;40, where f is a focal length of the optical imaging system, f6 is a focal length of the sixth lens, and V2 is an Abbe number of the second lens.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC 119(a) of Korean PatentApplication No. 10-2018-0076470 filed on Jul. 2, 2018 in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to an optical imaging system includingseven lenses.

2. Description of Background

Generally, small-sized cameras are mounted on wireless terminal devices.For example, a small-sized camera is generally mounted on the front andthe rear of a wireless terminal device. Such small-sized cameras areused for imaging outdoor scenery, people indoors, and the like, andthus, small-sized cameras are required to have performance similar tothat of general cameras. However, as there is a limitation in mountingspace of a small-sized camera in a wireless terminal device due to asize of the wireless terminal device, it may be difficult to implementhigh performance. Thus, it has been necessary to develop an opticalimaging system which can improve performance of a small-sized camerawithout increasing a size of the camera.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lenshaving positive refractive power and having a convex object-sidesurface; a second lens having negative refractive power; a third lenshaving refractive power; a fourth lens having refractive power; a fifthlens having refractive power; a sixth lens having positive refractivepower and having a convex image-side surface; and a seventh lens havingnegative refractive power and having a concave image-side surface. Thefirst to seventh lenses may be disposed in order from an object side. Inthe optical imaging system, 1<f/f6 and V2<40, where f is a focal lengthof the optical imaging system, f6 is a focal length of the sixth lens,and V2 is an Abbe number of the second lens.

An F No. of the optical imaging system may be 1.8 or less.

The optical imaging system may satisfy 0.05<OAL/HFOV<0.3, where OAL is adistance from an object-side surface of the first lens to an imagingplane, and HFOV is a half field of view of the optical imaging system.

The optical imaging system may satisfy 0.2<Th7/Th6<0.9, where Th6 is athickness of the sixth lens at an optical center, and Th7 is a thicknessof the seventh lens at an optical center.

The fourth lens may have negative refractive power.

The optical imaging system may include a stop disposed between the firstlens and the second lens.

The fifth lens may include an inflection point on one or both of anobject-side surface and an image-side surface of the fifth lens.

The sixth lens may include an inflection point on one or both of anobject-side surface and an image-side surface of the sixth lens.

The seventh lens may include an inflection point on one or both of anobject-side surface and an image-side surface of the seventh lens.

In another general aspect, an optical imaging system includes a firstlens, a second lens, a third lens, a fourth lens, a fifth lens, a sixthlens, and a seventh lens disposed in order from an object side. In theoptical imaging system, F No.<1.8 and V2<40, where V2 is an Abbe numberof the second lens.

The third lens may have positive refractive power.

The fourth lens may have negative refractive power.

The fifth lens may have positive refractive power.

The third lens may include a convex object-side surface.

The fourth lens may include a concave object-side surface.

The fifth lens, the sixth lens, and the seventh lens may each include aninflection point on one or both of a respective object-side surface anda respective image-side surface.

In another general aspect, an optical imaging system includes a firstlens, a second lens, a third lens, a fourth lens, a fifth lens, a sixthlens, and a seventh lens sequentially disposed from an object side to animage side. In the optical imaging system, the fourth lens includes oneconvex surface and one concave surface, and F No.<1.8.

The fourth lens may include a concave object-side surface and a conveximage-side surface.

The fourth lens may include a convex object-side surface and a concaveimage-side surface.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a first example of an optical imagingsystem.

FIG. 2 illustrates aberration curves of the optical imaging systemillustrated in FIG. 1 .

FIG. 3 is a diagram illustrating a second example of an optical imagingsystem.

FIG. 4 illustrates aberration curves of the optical imaging systemillustrated in FIG. 3 .

FIG. 5 is a diagram illustrating a third example of an optical imagingsystem.

FIG. 6 illustrates aberration curves of the optical imaging systemillustrated in FIG. 5 .

FIG. 7 is a diagram illustrating a fourth example of an optical imagingsystem.

FIG. 8 illustrates aberration curves of the optical imaging systemillustrated in FIG. 7 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

Herein, it is noted that use of the term “may” with respect to anexample or embodiment, e.g., as to what an example or embodiment mayinclude or implement, means that at least one example or embodimentexists in which such a feature is included or implemented while allexamples and embodiments are not limited thereto.

Throughout the specification, when an element, such as a layer, region,or substrate, is described as being “on,” “connected to,” or “coupledto” another element, it may be directly “on,” “connected to,” or“coupled to” the other element, or there may be one or more otherelements intervening therebetween. In contrast, when an element isdescribed as being “directly on,” “directly connected to,” or “directlycoupled to” another element, there can be no other elements interveningtherebetween.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as shown in the figures. Such spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,an element described as being “above” or “upper” relative to anotherelement will then be “below” or “lower” relative to the other element.Thus, the term “above” encompasses both the above and below orientationsdepending on the spatial orientation of the device. The device may alsobe oriented in other ways (for example, rotated 90 degrees or at otherorientations), and the spatially relative terms used herein are to beinterpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

Hereinafter, examples will be described with reference to the attacheddrawings.

In the examples, a first lens may refer to a lens disposed most adjacentto an object (or a subject), and a seventh lens may refer to a lensdisposed most adjacent to an imaging plane (or an image sensor). In theexamples, an entirety of a radius of curvature, a thickness, an OAL (adistance from an object-side surface of the first lens to the imagingplane), an ImgH (½ of an diagonal length of the imaging plane) and afocal length of a lens are indicated in millimeters (mm).

A thickness of a lens, a gap between lenses, and the OAL may bedistances at an optical axis of a lens. In a description of a form of alens, a surface of a lens being convex indicates that a paraxial regionof the surface is convex, while a surface of a lens being concaveindicates that a paraxial region of the surface is concave. Therefore,in a configuration in which a surface of a lens is described as beingconvex, an edge region of the lens may be concave. In a similar manner,in a configuration in which a surface of a lens is described as beingconcave, an edge region of the lens may be convex.

An optical imaging system may include seven lenses. For example, theoptical imaging system may include a first lens, a second lens, a thirdlens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. Thefirst to seventh lenses may be disposed with certain gaps. For example,image-side surfaces and object-side surfaces of adjacent lenses may notbe in contact with each other.

The first lens may have refractive power. For example, the first lensmay have positive refractive power. The first lens may have a convexsurface. For example, the first lens may have a convex object-sidesurface.

The first lens may include an aspherical surface. For example, bothsurfaces of the first lens may be aspherical. The first lens may be madeof a material having high light transmissivity and excellentworkability. For example, the first lens may be made of a plasticmaterial. The first lens may have a relative low refractive index. Forexample, a refractive index of the first lens may be less than 1.6.

The second lens may have refractive power. For example, the second lensmay have negative refractive power. The second lens may have a convexsurface. For example, the second lens may have a convex object-sidesurface.

The second lens may include an aspherical surface. For example, anobject-side surface of the second lens may be spherical. The second lensmay be made of a material having high light transmissivity and excellentworkability. For example, the second lens may be made of a plasticmaterial. The second lens may have a refractive index higher than arefractive index of the first lens. For example, a refractive index ofthe second lens may be 1.65 or higher.

The third lens may have refractive power. For example, the third lensmay have positive refractive power or negative refractive power. Thethird lens may have a convex surface. For example, the third lens mayhave a convex object-side surface.

The third lens may include an aspherical surface. For example, animage-side surface of the third lens may be aspherical. The third lensmay be made of a material having high light transmissivity and excellentworkability. For example, the third lens may be made of a plasticmaterial. The third lens may have a refractive index approximatelysimilar to a refractive index of the first lens. For example, arefractive index of the third lens may be less than 1.6.

The fourth lens may have refractive power. For example, the fourth lensmay have negative refractive power. The fourth lens may have a concavesurface. For example, an object-side surface or an image-side surface ofthe fourth lens may be concave.

The fourth lens may include an aspherical surface. For example, bothsurfaces of the fourth lens may be aspherical. The fourth lens may bemade of a material having high light transmissivity and excellentworkability. For example, the fourth lens may be made of a plasticmaterial. The fourth lens may have a refractive index higher than arefractive index of the first lens. For example, a refractive index ofthe fourth lens may be 1.6 or higher.

The fifth lens may have refractive power. For example, the fifth lensmay have positive refractive power or negative refractive power. Thefifth lens may have a convex surface. For example, an object-sidesurface of the fifth lens may be convex. The fifth lens may have a shapehaving an inflection point. For example, an inflection point may beformed on at least one of an object-side surface and an image-sidesurface of the fifth lens.

The fifth lens may include an aspherical surface. For example, bothsurfaces of the fifth lens may be aspherical. The fifth lens may be madeof a material having high light transmissivity and excellentworkability. For example, the fifth lens may be made of a plasticmaterial. The fifth lens may have a refractive index approximatelysimilar to a refractive index of the fourth lens. For example, arefractive index of the fifth lens may be 1.6 or higher.

The sixth lens may have refractive power. For example, the sixth lensmay have positive refractive power. The sixth lens may have at least oneconvex surface. For example, an object-side surface or an image-sidesurface of the sixth lens may be convex, or both surfaces of the sixthlens may be convex. The sixth lens may have a shape having an inflectionpoint. For example, an inflection point may be formed on at least one ofan object-side surface and an image-side surface of the sixth lens.

The sixth lens may include an aspherical surface. For example, bothsurfaces of the sixth lens may be aspherical. The sixth lens may be madeof a material having high light transmissivity and excellentworkability. For example, the sixth lens may be made of a plasticmaterial. The sixth lens may have a refractive index lower than arefractive index of the fifth lens. For example, a refractive index ofthe sixth lens may be less than 1.6.

The seventh lens may have refractive power. For example, the seventhlens may have negative refractive power. The seventh lens may have atleast one concave surface. For example, an object-side surface or animage-side surface of the seventh lens may be concave, or both surfacesof the seventh lens may be concave. The seventh lens may have a shapehaving an inflection point. For example, an inflection point may beformed on at least one of an object-side surface and an image-sidesurface of the seventh lens.

The seventh lens may include an aspherical surface. For example, bothsurfaces of the seventh lens may be aspherical. The seventh lens may bemade of a material having high light transmissivity and excellentworkability. For example, the seventh lens may be made of a plasticmaterial. The seventh lens may have a refractive index approximatelysimilar to a refractive index of the sixth lens. For example, arefractive index of the seventh lens may be less than 1.6.

The aspherical surfaces of the first to seventh lenses may berepresented by Equation 1 below.

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Ir}^{20}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, “c” is an inverse of a radius of a curvature of arespective lens, “K” is a conic constant, “r” is a distance from acertain point on an aspherical surface of the lens to an optical axis,“A” to “H” are aspheric constants, and “Z” (or SAG) is a height from acertain point on an aspherical surface of the lens to an apex of theaspherical surface in an optical axis direction.

The optical imaging system may further include a filter, an imagesensor, and a stop.

The filter may be disposed between the seventh lens and an image sensor.The filter may block light having a certain wavelength. For example, thefilter may block light having an infrared wavelength.

The image sensor may form an imaging plane. For example, a surface ofthe image sensor may form the imaging plane.

The stop may be disposed to adjust the amount of light incident to alens. For example, the stop may be disposed between the first lens andthe second lens or between the second lens and the third lens.

The optical imaging system may satisfy conditional expressions below:1.0<f/f6  (Conditional Expression 1)V2<40  (Conditional Expression 2)F No.<1.8  (Conditional Expression 3)0.05<OAL/HFOV<0.3  (Conditional Expression 4)0.2<Th6/Th7<0.9  (Conditional Expression 5)

In the conditional expressions, “f” is a length of the optical imagingsystem, “f6” is a focal length of the sixth lens, “V2” is an Abbe numberof the second lens, “OAL” is a distance from an object-side surface ofthe first lens to an imaging plane, “HFOV” is a half field of view ofthe optical imaging system, “Th6” is a thickness of the sixth lens at anoptical center, and “Th7” is a thickness of the seventh lens at anoptical center.

In the description below, an optical imaging system will be described inaccordance with examples.

embodiment first example of an optical imaging system will be describedwith reference to FIG. 1 .

The optical imaging system 100 may include a first lens 110, a secondlens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixthlens 160, and a seventh lens 170.

The first lens 110 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 120 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 130may have positive refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 140 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 150 may have positiverefractive power, and may have a convex object-side surface and aconcave image-side surface. The fifth lens 150 may have a shape in whichan inflection point is formed on an object-side surface and animage-side surface of the fifth lens 150. The sixth lens 160 may havepositive refractive power, and may have a convex object-side surface anda convex image-side surface. The sixth lens 160 may have a shape inwhich an inflection point is formed on an object-side surface and animage-side surface of the sixth lens 160. The seventh lens 170 may havenegative refractive power, and may have a concave object-side surfaceand a concave image-side surface. The seventh lens 170 may have a shapein which an inflection point is formed on an object-side surface and animage-side surface of the seventh lens 170.

The optical imaging system 100 may further include a filter 180, animage sensor 190, and a stop ST. The filter 180 may be disposed betweenthe seventh lens 170 and the image sensor 190, and the stop ST may bedisposed between the first lens 110 and the second lens 120.

The optical imaging system 100 may include a plurality of lenses havingrelatively high refractive indexes. For example, the second lens 120,the fourth lens 140, and the fifth lens 150 may have a refractive indexof 1.6 or higher.

The optical imaging system 100 may have aberration characteristics asillustrated in FIG. 2 . Table 1 lists characteristics of the lenses ofthe optical imaging system 100. In the optical imaging system 100 ofFIG. 1 , a focal length is 4.210, and a total field of view is 78.8.

TABLE 1 Radius Thick- Refrac- Surface of Cur- ness/ tive Abbe Focal No.Note vature Distance Index No. Length 1 First 1.834 0.835 1.544 56.14.290 2 Lens 7.092 0.071 3 Second 4.808 0.200 1.671 19.25 −12.58 (Stop)Lens 4 3.022 0.339 5 Third 10.000 0.385 1.544 56.1 20.468 6 Lens 93.8780.144 7 Fourth −6.012 0.210 1.633 23.9 −10.86 8 Lens −45.022 0.058 9Fifth 2.511 0.240 1.633 23.9 70.833 10 Lens 2.559 0.319 11 Sixth 9.0140.653 1.544 56.1 2.343 12 Lens −1.453 0.360 13 Seventh −3.013 0.3701.544 56.1 −2.095 14 Lens 1.924 0.186 15 Filter Infinity 0.210 1.51764.2 16 Infinity 0.660 17 Imaging Infinity Plane

A second example of an optical imaging system will be described withreference to FIG. 3 .

The optical imaging system 200 may include a first lens 210, a secondlens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixthlens 260, and a seventh lens 270.

The first lens 210 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 220 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 230may have positive refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 240 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 250 may have positiverefractive power, and may have a convex object-side surface and aconcave image-side surface. The fifth lens 250 may have a shape in whichan inflection point is formed on an object-side surface and animage-side surface of the fifth lens 250. The sixth lens 260 may havepositive refractive power, and may have a convex object-side surface anda convex image-side surface. The sixth lens 260 may have a shape inwhich an inflection point is formed on an object-side surface and animage-side surface of the sixth lens 260. The seventh lens 270 may havenegative refractive power, and may have a concave object-side surfaceand a concave image-side surface. The seventh lens 270 may have a shapein which an inflection point is formed on an object-side surface and animage-side surface of the seventh lens 270.

The optical imaging system 200 may further include a filter 280, animage sensor 290, and a stop ST. The filter 280 may be disposed betweenthe seventh lens 270 and the image sensor 290, and the stop ST may bedisposed between the first lens 210 and the second lens 220.

The optical imaging system 200 may include a plurality of lenses havingrelatively high refractive indexes. For example, the second lens 220,the fourth lens 240, and the fifth lens 250 may have a refractive indexof 1.6 or higher.

The optical imaging system 200 may have aberration characteristics asillustrated in FIG. 4 . Table 2 lists characteristics of the lenses ofthe optical imaging system 200. In the optical imaging system 200 ofFIG. 3 , a focal length is 4.220, and a total field of view is 78.5.

TABLE 2 Radius Thick- Refrac- Surface of Cur- ness/ tive Abbe Focal No.Note vature Distance Index No. Length 1 First 1.812 0.835 1.544 56.14.268376 2 Lens 6.820 0.113 3 Second 4.68264 0.200 1.671 19.25 −12.69996(Stop) Lens 4 2.980 0.327 5 Third 10.000 0.410 1.544 56.1 22.384065 6Lens 54.244 0.135 7 Fourth −6.109 0.210 1.633 23.9 −13.34233 8 Lens−21.731 0.039 9 Fifth 2.88075 0.240 1.633 23.9 62.169594 10 Lens 3.004520.307 11 Sixth 8.647 0.704 1.544 56.1 2.434597 12 Lens −1.525 0.303 13Seventh −3.741 0.370 1.544 56.1 −2.083672 14 Lens 1.692 0.177 15 FilterInfinity 0.210 1.517 64.2 16 Infinity 0.660 17 Imaging Infinity Plane

A third example of an optical imaging system will be described withreference to FIG. 5 .

The optical imaging system 300 may include a first lens 310, a secondlens 320, a third lens 330, a fourth lens 340, a fifth lens 350, a sixthlens 360, and a seventh lens 370.

The first lens 310 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 320 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 330may have positive refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 340 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 350 may have positiverefractive power, and may have a convex object-side surface and aconcave image-side surface. The fifth lens 350 may have a shape in whichan inflection point is formed on an object-side surface and animage-side surface of the fifth lens 350. The sixth lens 360 may havepositive refractive power, and may have a convex object-side surface anda convex image-side surface. The sixth lens 360 may have a shape inwhich an inflection point is formed on an object-side surface and animage-side surface of the sixth lens 360. The seventh lens 370 may havenegative refractive power, and may have a concave object-side surfaceand a concave image-side surface. The seventh lens 370 may have a shapein which an inflection point is formed on an object-side surface and animage-side surface of the seventh lens 370.

The optical imaging system 300 may further include a filter 380, animage sensor 390, and a stop ST. The filter 380 may be disposed betweenthe seventh lens 370 and the image sensor 390, and the stop ST may bedisposed between the first lens 310 and the second lens 320.

The optical imaging system 300 may include a plurality of lenses havingrelatively high refractive indexes. For example, the second lens 320,the fourth lens 340, and the fifth lens 350 may have a refractive indexof 1.6 or higher.

The optical imaging system 300 may have aberration characteristics asillustrated in FIG. 6 . Table 3 lists characteristics of the lenses ofthe optical imaging system 300. In the optical imaging system 300 ofFIG. 5 , a focal length is 4.230, and a total field of view is 78.1.

TABLE 3 Thick- Radius ness/ Refrac- Surface of Cur- Dis- tive Abbe FocalNo. Note vature tance Index No. Length 1 First 1.804 0.798 1.544 56.14.195062 2 Lens 7.179 0.156 3 Second 4.78881 0.210 1.671 19.25 −11.75658(Stop) Lens 4 2.938 0.320 5 Third 10.000 0.419 1.544 56.1 23.898276 6Lens 42.188 0.112 7 Fourth −5.865 0.210 1.633 23.9 −14.74893 8 Lens−15.698 0.041 9 Fifth 3.17781 0.255 1.651 21.5 100.586 10 Lens 3.232270.293 11 Sixth 9.727 0.716 1.544 56.1 2.457922 12 Lens −1.516 0.332 13Seventh −3.605 0.350 1.544 56.1 −2.122495 14 Lens 1.766 0.169 15 FilterInfinity 0.210 1.517 64.2 16 Infinity 0.660 17 Imaging Infinity Plane

A fourth example of an optical imaging system will be described withreference to FIG. 7 .

The optical imaging system 400 may include a first lens 410, a secondlens 420, a third lens 430, a fourth lens 440, a fifth lens 450, a sixthlens 460, and a seventh lens 470.

The first lens 410 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 420 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 430may have positive refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 440 may havenegative refractive power, and may have a convex object-side surface anda concave image-side surface. The fifth lens 450 may have positiverefractive power, and may have a convex object-side surface and aconcave image-side surface. The fifth lens 450 may have a shape in whichan inflection point is formed on an object-side surface and animage-side surface of the fifth lens 450. The sixth lens 460 may havepositive refractive power, and may have a convex object-side surface anda convex image-side surface. The sixth lens 460 may have a shape inwhich an inflection point is formed on an object-side surface and animage-side surface of the sixth lens 460. The seventh lens 470 may havenegative refractive power, and may have a concave object-side surfaceand a concave image-side surface. The seventh lens 470 may have a shapein which an inflection point is formed on an object-side surface and animage-side surface of the seventh lens 470.

The optical imaging system 400 may further include a filter 480, animage sensor 490, and a stop ST. The filter 480 may be disposed betweenthe seventh lens 470 and the image sensor 490, and the stop ST may bedisposed between the first lens 410 and the second lens 420.

The optical imaging system 400 may include a plurality of lenses havingrelatively high refractive indexes. For example, the second lens 420,the fourth lens 440, and the fifth lens 450 may have a refractive indexof 1.6 or higher.

The optical imaging system 400 may have aberration characteristics asillustrated in FIG. 8 . Table 4 lists characteristics of the lensesoptical imaging system 400. In the optical imaging system 400 of FIG. 7, a focal length is 4.30, and a total field of view is 77.5.

TABLE 4 Radius Thick- Refrac- Surface of Cur- ness/ tive Abbe Focal No.Note vature Distance Index No. Length 1 First 1.804 0.820 1.544 56.14.545884 2 Lens 5.544 0.095 3 Second 4.12697 0.200 1.671 19.25 16.00356(Stop) Lens 4 2.930 0.361 5 Third 18.510 0.367 1.544 56.1 754.84395 6Lens 19.245 0.098 7 Fourth 5.245 0.210 1.657 20.4 44.71198 8 Lens 4.3890.183 9 Fifth 5.52469 0.254 1.613 26 1001.212 10 Lens 5.47636 0.274 11Sixth 7.190 0.560 1.544 56.1 3.038635 12 Lens −2.097 0.488 13 Seventh−5.355 0.350 1.544 56.1 2.551526 14 Lens 1.926 0.180 15 Filter Infinity0.110 1.517 64.2 16 Infinity 0.640 17 Imaging Infinity Plane

Table 5 lists values of the conditional expressions of the opticalimaging systems of the first to fourth examples.

TABLE 5 Conditional First Second Third Fourth Expressions ExampleExample Example Example f/f6 1.797 1.733 1.721 1.415 V2 23.90 23.9023.90 20.40 F No 1.580 1.580 1.580 1.580 OAL/HFOV 0.133 0.134 0.1340.134 Th7/Th6 0.567 0.525 0.489 0.625

The optical imaging system of the examples may have opticalcharacteristics as discussed below. For example, a focal lengths of theoptical imaging system may be within a range of 4.0 mm to 4.5 mm, atotal length TTL may be within a range of 5.0 mm to 5.5 mm, a totalfield of view (FOV) may be within a range of 70° to 80°, a focal lengthof the first lens may be within a range of 4.0 mm to 5.0 mm, a focallength of the second lens may be within a range of −20 mm to −10 mm, afocal length of the third lens may be 18 mm or greater, a focal lengthof the fourth lens may be −8 mm or lower, a focal length of the fifthlens may be 50 mm or greater, a focal length of the sixth lens may bewithin a range of 2.0 mm to 4.0 mm, and a focal length of the seventhlens may be within a range of −3.0 mm to −1.5 mm.

According to the aforementioned examples, the optical imaging system mayimprove performance of a small-sized camera.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system, comprising: a firstlens having positive refractive power and comprising a convexobject-side surface and a concave image-side surface at an optical axisof the optical imaging system; a second lens having negative refractivepower; a third lens having refractive power, and a focal length equal toor greater than 18 mm; a fourth lens having refractive power andcomprising a convex image-side surface at the optical axis of theoptical imaging system; a fifth lens having positive refractive power,and a focal length equal to or greater than 50 mm; a sixth lens havingpositive refractive power and comprising a convex image-side surface;and a seventh lens having negative refractive power and comprising aconcave image-side surface, wherein the first to seventh lenses aredisposed in order from an object side to an imaging side, and wherein:1<f/f6V2<40, where f is a focal length of the optical imaging system, f6 is afocal length of the sixth lens, and V2 is an Abbe number of the secondlens.
 2. The optical imaging system of claim 1, wherein an F No. is 1.8or less.
 3. The optical imaging system of claim 1, wherein:0.05<OAL/HFOV<0.3, where OAL is a distance, in millimeters, from anobject-side surface of the first lens to an imaging plane, and HFOV is ahalf field of view, in degrees, of the optical imaging system.
 4. Theoptical imaging system of claim 1, wherein:0.2<Th7/Th6<0.9, where Th6 is a thickness of the sixth lens at anoptical center, and Th7 is a thickness of the seventh lens at an opticalcenter.
 5. The optical imaging system of claim 1, wherein the fourthlens has negative refractive power.
 6. The optical imaging system ofclaim 1, further comprising a stop disposed between the first lens andthe second lens.
 7. The optical imaging system of claim 1, wherein thefifth lens comprises an inflection point on one or both of anobject-side surface and an image-side surface of the fifth lens.
 8. Theoptical imaging system of claim 1, wherein the sixth lens comprises aninflection point on one or both of an object-side surface and animage-side surface of the sixth lens.
 9. The optical imaging system ofclaim 1, wherein the seventh lens comprises an inflection point on oneor both of an object-side surface and an image-side surface of theseventh lens.
 10. The optical imaging system of claim 1, wherein thefifth lens comprises a convex object-side surface at the optical axis ofthe optical imaging system.
 11. The optical imaging system of claim 10,wherein the seventh lens comprises a concave object-side surface at theoptical axis of the optical imaging system.
 12. The optical imagingsystem of claim 1, wherein the third lens comprises a convex object-sidesurface and a concave image-side surface.
 13. The optical imaging systemof claim 1, wherein the third lens has a positive refractive power. 14.The optical imaging system of claim 1, wherein a thickness along anoptical axis of the first lens is greater than a distance between theimage-side surface of the sixth lens and an object-side surface of theseventh lens along the optical axis.
 15. An optical imaging system,comprising: a first lens comprising a concave image-side surface at anoptical axis of the optical imaging system, a second lens, a third lenshaving a focal length equal to or greater than 18 mm, a fourth lenscomprising a convex image-side surface at the optical axis of theoptical imaging system, a fifth lens having positive refractive power,and a focal length equal to or greater than 50 mm, a sixth lens, and aseventh lens disposed in order from an object side to an imaging side,wherein:F No.<1.8V2<40, where V2 is an Abbe number of the second lens, and wherein athickness along an optical axis of the first lens is greater than adistance between the image-side surface of the sixth lens and anobject-side surface of the seventh lens along the optical axis.
 16. Theoptical imaging system of claim 15, wherein the third lens has positiverefractive power.
 17. The optical imaging system of claim 15, whereinthe fourth lens has negative refractive power.
 18. The optical imagingsystem of claim 15, wherein the third lens comprises a convexobject-side surface.
 19. The optical imaging system of claim 15, whereinthe fourth lens comprises a concave object-side surface at an opticalaxis of the optical imaging system.
 20. The optical imaging system ofclaim 15, wherein the fifth lens, the sixth lens, and the seventh lenseach comprise an inflection point on one or both of a respectiveobject-side surface and a respective image-side surface.
 21. An opticalimaging system, comprising: a first lens comprising a concave image-sidesurface at an optical axis of the optical imaging system; a second lenscomprising a refractive power; a third lens comprising a refractivepower, and a focal length equal to or greater than 18 mm; a fourth lenscomprising a convex image-side surface at the optical axis of theoptical imaging system; a fifth lens comprising a refractive power, anda focal length equal to or greater than 50 mm; a sixth lens comprising arefractive power; and a seventh lens comprising a refractive power,wherein the first to seventh lenses are sequentially disposed in orderfrom an object side to an imaging side, wherein F No.<1.8 and V2<40,where V2 is an Abbe number of the second lens, and wherein a radius ofcurvature of an object-side surface of the fifth lens is greater than aradius of curvature of an object-side surface of the fourth lens.